Roasting separation process.



- ways.

UNITED STATES. PATENT orrron.

HENRY AZOR WENTWORTI-I, OF NEWTON, MASSACHUSETTS, ASSIGNOR TO HUFI I ELECTROSTATIC SEPARATOR COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORA- TION OF MAINE.

No Drawing.

To all whom it may concern:

Be it known that'I, IIENRY Azon ENT-e WORTH, a citizen of the United States, and resident of Newton, in the county of Mid- (llesex and State of Massachusetts, have invented new and useful Improvements in fioastingfleparation Processes, of which the following is a specification.

-My invention relates to the separation of the ingredients which constitute ore mixtures and particularly to the separation of sulfid ores from each other.

Various separat-ive processes have been applied to the work of segregating sulfids from the gangue minerals such as quartz, limestone, garnet etc. with which they are found associated, and so far as the separation of the sulfids from the gangue is concerned, no very difficult, certainly no insuperable problem is presented to those skilled in the art of separation in its present day condition. \Vhen it comes, however, to the separation of one sulfid. from another, the situation is diiferent and processes which successfully segregate sulfids from gangue are in practice incapable of separating many sulfids from one another. There are large bodies of ore in Colorado, Montana, New Mexico and elsewhere from which the sulfids can be separated commercially as a whole from the gangue materials, but in which the separation of some of the sulfids from one another has not proved commercially practicable by known existing methods. In almost all ores of this character it is of particular importance that zinc sulfids (either blende or marmatite) be separated mechanically from sulfids of lead, iron, and copper, some or all of which are found accompanied by zinc sulfid.

By experimentation with many mineral substances 1 have found that there are pronounced differences in respect to the surface tension effect of a liquid upon various materials and that as a rule metallic oxids or sulfates are sustained not at all or are sustained comparatively feebly by liquid ten sion as contrasted with the crystalline sulfids of the same bases. These differentiating surfacetension effects are manifested in various Finely comminuted metallic sulfids if gently deposited upon the surface of water are readily sustained thereby, whereas oxids or sulfids become quite readily superficially Specification of Letters Patent.

wetted and sink beneath the surface. Also ROASTING SEPARATION PROCESS,

Patented Nov. 2, 1909.

Application filed January 2, 1909. Serial No. 470,404.

if oil is agitated in contact with metallic oxids or sulfates, it does not adhere to them so readily as it does to the sulfids of the same metals; if mixtures of minerals are treated as a wet pulp with a warm dilute solution of acid or acid salt, causing the formation of bubbles of gas, these bubbles selectively attach themselves to sulfid particles and do not become readily attached to particles of oxide or sulfates. Such phenomena as these appear to demonstrate that-the sulfids have in general a much feeble]? superficial attraction for water or liquids in which water is an important ingredient than do oxids 01' sulfates, and that when immersed the oxids or sulfates are so intimately associated with-contacting water molecules'that the attachment of bubbles to these solids is resisted whereas even though immersed, sultid particles lie in less intimate contact with water so that gas bubbles insinuate themselves, as it were, be-. tween the water and the sulfid particles, clinging to the latter and buoying it up. fits to the difference in aflinity for oily substances, the contrast between sulfids on the one hand, and oxids or sulfates. on the other, may demonstrate that for'oily liquids the sulfids possess a stronger superficial aflinity than do the other salts.

Whatever may be the true explanation of the differences between the behavior of sulfids and oxids, sulfates or whatever may be formed of some of the sulfids by heat these phenomena have at least demonstrated that mixtures containing a sulfid and also oxids,

sulfates or their compounds can be separated by flotation processes.

My process herein described conslsts in a preliminary treatment of ore mixtures containing several sulfids, which converts some of the sulfids superficially atleast into metallic salts which are differentiated fromthe sulfids in their behavior with respect to su perficial adhesion of a liquid, and thereafter subjecting the ,mixture thus prepared to a separative flotation which may be of one or another specific character. The prellmlnary treatment so affects some sulfids as to relegate them to the same class as that naturally occupied by the ganguematerials 1n respect to the flotation separation to be next employed. As a specific illustration I take an ore which contains zinc sulfid, lead sulfid, copper sulfid, iron sulfid and rock or gangue. Such a mixture being first comminuted so as I to physically free the-several ingredients one from another, is then subjected to a roasting at such a 'tem erature and for such time that the zlnc sulfi particles are not appreciably afi'ected, if they. are afiected at all, while the other sulfids are superficially at" least, changed in chemical character, converted perhaps into oxide or sulfates, or both. Ordinarily to accomplish this result a roasting for but a few minutes at a temperature to give a dull red heat' will be found suflicient.

After roasting, the mass of comminuted, particles is cooled and then put into contact accompanied by agitation with an oil such as crude mineral oil, with possibly a small proportion of acid, such as sulfuric acid, whereuponthe oil selectively attaches itself to the zinc 'sulfid particles leaving the particles of I the altered ingredients substantially untouched. The mass of material is then passed through or upon a surface of water which floats the oil coated zinc sulfid particles while the other particles comprising metallic salts and gangue, sink; this operation permits the separation and collection of the floated sulfid onthe one hand and those ingredients which have been precipitated on the other.

The oil flotation treatment is mentioned merelyas a specific instance of one kind of flotation separation which maybe employed to segregate those particles which have been affected by the preliminary heating or roasting from those which have passed through the preliminary stage without being sensibly affected. As the flotation separation depends principally upon the selective effects of liquid film tension or adhesion, other specific and well known flotation processes may'be employed when appropriate, onmay be adopted as asuitable alternative for a process involving the employment oi oil.

The apparatus required for the performance of the above described process need not be described in detail for the reasonthat many forms of roasting ovens now in use are suited to the preliminary treatment of ores containing several metallic sulfids; also the agitating'vessels now in use in oil flotation processes are ada ted to the treatment of the ore mixtures di 'erentially aifected by the preliminary roasting; also the flotation tanks and collecting ap aratus now in use may- 'from iron sulfid, copper sulfid, and lead. 'sul fid, which consists in subjecting the mixture to a roasting to an intensity sufficient to at least superficially oxidize the sulfids other than zinc sulfid, while insuflicient materially to affect the zinc sulfid, and thereafter separating the zinc sulfid from the other ingredients by flotation. Signed-by me at Boston, Massachusetts this twenty-eighth day of December1908.

HENRY zon wun r'wonrufi Witnesses:

CHARLES D. WoonBERRY, 1 JOSEPHINE H. RYAN. 

